The present in vent ion relates to microencapsulated insecticide compositions which are stabilized against environmental degradation. The present invention more specifically relates to microencapsulated chlorpyrifos or endosulfan stabilized against degradation by visible and ultra-violet light having unexpected extended insecticidal activity while having unexpected low toxicity to non-target species.
Chlorpyrifos, which is the common name for O,O-diethyl-O-(3,5,6-trichloro-2-pyridyl)-phosphorathio- ate, is a well-known insecticide. Two major problems of this insecticide is on the one hand its ease of decomposition when exposed to the environment and the concomitant high toxicity to non-target animals. Thus, technical chlorpyrifos has a toxicity to rats (acute oral) of an LD.sub.50 of 168 mg/kg and a toxicity to trout (acute) of an LC.sub.50 of 0.007 mg/kg.
Endosulfan, which is the common name for 6,7,8,9,10-hexachloro-1,5-5a,9a tetryhydro-6,9-methano-2,4,3-benzodioxathipia-3-oxide, is also a well-known insecticide, with stability and toxicity problems. Its toxicity problem is most acute to non-target species such as fish and bees as the technical material has an LD.sub.50 to non-target species such as mice of 30 mg/kg. For an EC formulation to classified as "only harmful" its LD.sub.50 to mice must be at least 200 mg/kg. However, to reach such a toxicity, the concentration of endosulfan must be dropped to 3%, resulting in a non-economical mixture of very low activity.
The microencapsulation of pesticides and insecticides has been proposed in the prior art as a way of extending the insecticidal life of pesticides while supposedly decreasing their toxicity to non-target animals. Examples are: U.S. Pat. Nos. 2,800,458; 3,069,370 , 3,116,216, 3,137,631, 3,270,100; 3,418,250; 3,429,827; 3,577,515; 3,959,164; 4,417,916; and 4,563,212. British Patent Number 1,371,179; European Patent Publication Numbers 148,169 and 165,227; and Israel Patent Numbers 79,575 and 84,910.
Microencapsulated chlorpyrifos has been reported in European Patent Application No. 140,548. Microencapsulated endosulfan has been reported in U.S. Pat. No. 4,230,809. in neither case is there any report of the use of ultraviolet absorbers in these microencapsulated formulations.
The use of an ultraviolet absorber to protect insecticides, especially pyrethroids, has been reported in U.S. Pat. Nos. 2,168,064; 3,063,893; 3,098,000; 3,130,121; 3,264,176; 3,541,203; 3,560,613; and 3,839,561.
U.S. Pat. Nos. 4,056,610 and 4,497,793 describe the use of specific UV absorbers in microencapsulated pyrethrins. However, these require the case of U.S. Pat. No. 4,056,610--the use of a UV absorber both the outer casing and in the liquid fill.
Regardless of the disclosure in the prior art, there has not yet been offered for sale microencapsulated chlorpyrifos or endosulfan, which has both extended insecticidal activity and extremely low toxicity to non-target animals.